The most important thing for you to do would be to start exam preparation if you haven't already. (And before I have 13,000 kids freak out... I don't mean do 50 practice exams, I mean start studying like you were studying for the exam... because you are).
So, I just plugged in 37 to all of your subjects on ATAR Calc, and it told me that would get you an 83 ATAR, so that's probably about what you should be realistically striving for. So, you'd need As/A+s on your exams in order to safely achieve those scores. So I'd find out what it takes to get an A in terms of marks in any given subject, (i.e., "Okay, I need 73% in the Legal Studies exam to get an A"), and that gives you a measure of how well you should know the content. For example, take a Legal Studies exam right now on only the things you've studied and I promise you that you will get slaughtered. Get your teacher to mark it - you'll probably get like 50%. That will give you an idea of the level you need to be at. From then on, when you revise, you can revise a concept until the point that you believe you would be x% on the exam, if the exam were ONLY on that topic. (In fact, this would be silly - you should revise concepts until you believe that, if that were the only concept tested on the exam, you could get 100%. If you move on prior to this point, you haven't revised properly. If you get 73% on the exam, it should only because you made 27% worth of mistakes in the moment, and not because you skipped something in revision).
So yeah, you can totally get an ATAR, but you need to get serious about the way you study, because looking at your SAC grades, they're actually really high scores. But you say your school is not great and that these scores are 'average', so I can only assume there are lots of people getting these scores, which tells me your SACs are easy - which further tells me that a lot of people are going to get shitty study scores, because they're going to assume that they're geniuses and don't need to revise for the exam. I was in a school like this, haha. Just make sure you really revise properly, and revise like you were going to sit the exam only on each topic. Worked for me, and I think it's a method that really makes sense.